The M16 automatic rifle is a standard weapon of choice for many institutions around the world including the U.S. military and many law enforcement agencies. Over the years the M16 has been modified to include a large family of weapons including semi-automatic counterparts which are popular in the civilian sector. Generally, the M16 family of automatic and semi-automatic rifles is based on a gas operated rotating bolt carrier system. The bolt carrier includes a multi-lug bolt that interlocks with corresponding lugs within a barrel extension engaged to the barrel to contain the firing of each round of ammunition. The bolt carrier system includes a rotating mechanism that locks the bolt into place with respect to the barrel extension during the loading step and also includes a corresponding unlocking motion when extracting a spent casing. The bolt includes a spring loaded extractor configured to releasably engage a cartridge as it is loaded into the firing chamber. When the rifle is fired the interlock bolt contains the firing force by transmitting the force through the lugs to corresponding lugs of the barrel extension.
When a round is fired, gas pressure is vented from a port in the barrel down from the firing chamber and that gas pressure is applied to the bolt carrier system to impart energy in a rearward direction. As the bolt carrier system moves rearwardly it first rotates the bolt to unlock the bolt lugs from the barrel extension lugs. Then, as it further recoils, the extractor pulls the expended cartridge from the firing chamber. Once the cartridge clears the firing chamber an ejector in the bolt pivots the cartridge about the extractor and ejects the spent cartridge as is well known in the art. As the bolt carrier system continues to move rearwardly its travel is halted by a spring that then pushes the bolt carrier system forward to engage and chamber another round. This process is repeated as often as desired by a shooter until the last cartridge in a magazine is expended.